1. Field of the Invention
The present invention is directed to an arrangement for preventing the admission of alien substances into the space between a shaft and its bearing section where no lubricant, such as oil or water, is used in the space.
2. Description of the Prior Art
In machine tools and automobile engines, it is often noticed that alien substances find their way into the space between a shaft and its bearing and result in malfunctioning. For example, in a throttle shaft bearing for a carburetor in an automobile engine, it is possible that the atmosphere surrounding the carburetor may be cooled to a temperature below the dew point as a result of the gasoline vaporization heat generated during operation of the engine, and, consequently, moisture contained in the mixture may condense and form water droplets which enter the bearing section of the throttle shaft. If the atmospheric temperature falls below the freezing point when the engine is not in use, the water droplets freeze and may damage the bearing and render the engine inoperable. Further, if such a situation exists over a period of time, the bearing rusts and becomes inoperative.
Further, in an exhaust gas recirculation system which has been developed recently as an exhaust gas cleaning means, if the recirculation gas is introduced into the carburetor from a point above its throttle valve, any moisture contained in the recirculation gas may be condensed on the throttle valve and enter into the space between the valve shaft and its bearing causing problems as mentioned above.